Conventionally, a charge coupled device (CCD) and a semiconductor element of a complementary metal oxide semiconductor (CMOS) structure are mainly used as an imaging element (image sensor). Further, in recent years, an imaging element is proposed which uses an organic photoelectric conversion element whose photoelectric conversion layer is formed of an organic semiconductor material (for example, see Patent Documents 1 to 5). The organic photoelectric conversion element has characteristics that a color filter is not required and a structure and a manufacturing process can be simplified as compared with a conventional inorganic semiconductor element.
Specifically, Patent Document 1 discloses a color sensor having a structure in which a first organic dye layer and a second organic dye layer are provided between a first conductive material and a second conductive material and a third conductive material is provided between these organic dye layers. Patent Documents 2 to 4 disclose an imaging element having a structure in which two or three types of light receiving portions formed of an organic photoelectric material having an absorption peak at a wavelength corresponding to R (red), G (green), or B (blue) are laminated.
Each of the imaging elements described in Patent Documents 2 to 4 is provided with a pair of electrodes for each light receiving portion. On the other hand, Patent Document 5 discloses a photoelectric conversion element having a structure in which a plurality of organic photoelectric conversion films having different absorption spectra are laminated between a pair of electrodes. An imaging element described in Patent Document 5 controls a range from which charge is extracted and switches a wavelength region to be detected by changing a voltage applied between the pair of electrodes.